Plate heat exchanger with reinforced covers and method for the production of said reinforced covers and their assembly

ABSTRACT

A plate heat exchanger includes a pack of superimposed heat exchanger plates, and has two cover plates mounted on the side portions of the first heat exchanger plate. The surface area of each of the two cover plates is smaller than half of the surface area of said first heat exchanger plate.

The present patent relates to plate heat exchangers and in particular concerns a new plate heat exchanger with reinforced cover plates and method for the production of said reinforced cover plates and their assembly.

The prior art includes plate heat exchangers comprising at least two separate circuits respectively for the circulation of a primary fluid and a secondary fluid, where those circuits are defined by a plurality of exchange plates with facing surfaces, featuring ridges and depressions, generally distributed in a herringbone pattern.

The heat exchangers of the prior art are made by stacking the plates in question alternating the rotation of every other one by 180° so that the ridges and depressions of one plate are crossed with respect to the ridges and depressions of the adjacent plate.

Usually the plates are called symmetric when the ridges and depressions are such that the sections of the channels of both paths used by the two fluids are substantially equal, that is, resulting in equal flow resistance with equal flows.

These kinds of heat exchangers are commonly used to heat water for domestic use using the hot fluid of the heating system.

Prior art also includes specially shaped plates such that the section for the heating water is wider than that used for the domestic water system and therefore the flow resistance is differentiated.

For this purpose the prior art includes so-called asymmetric heat exchangers, that is, formed by plates comprising ridges with a different shape than the depressions, such as, for example, flat ridges to make the section of the channel even wider.

Plates having different flow resistances with equal flows are also known, obtained by increasing the pitch of the ridges, that is, the distance between the ridges of two adjacent channels. This type of heat exchanger is suitable for the exchange between water and cooling fluid, where the water flows through the circuit having lower flow resistance. In this case the plates are not rotated 180°, but alternate with each other as they have two different configurations.

Regardless of the size and depth of the ridges and depressions, the intermediate exchange plates of heat exchangers of the prior art are normally made of very thin metal sheets, usually steel or other material suitable for the manufacturing of heat exchangers.

The heat exchanger pack is closed by a cover plate which has a shape corresponding to the exchange plates, and is equipped with water inlet and outlet holes and holes for the connection to the system's piping.

Said cover plate is generally more rigid, usually made of steel sheet and may have a corrugated surface, that is, with ridges and depressions, which further increase its stiffness, or an essentially flat surface.

The function and purpose of the cover plate is to withstand the pressure exerted by the fluids towards the outside, to house the connections to the boiler unit, and to create the seat for the fastening systems, such as stud bolts, fittings or the like.

There is currently a need to minimize the weight of boiler units and the use of raw materials. For this purpose, there are corrugated cover plates in the prior art which also work as exchange plates, thus being able to reduce the number of intermediate exchange plates.

Document CN101184574 A relates to a plate heat exchanger comprising adapter plates installed between the cover plate and the inlets and outlets of the system. Each of said adapter plates has two holes for the connection with the heat exchanger plates. On the face of said adapter plates intended to be coupled to the outer side of the cover plate, there are depressions intended to be filled with welding material for the subsequent joining to the cover plate itself.

The object of the present patent is a new plate heat exchanger with reinforced cover plates and a method for producing said reinforced cover plates and their assembly.

The main object of the present invention is to decrease the weight of the heat exchanger, minimizing the weight of the cover plate.

Another important object of the present invention is to speed up the procedures for manufacturing and assembling the heat exchanger, thanks to the fact that it is possible to eliminate some welding steps in a preferred embodiment. The cover plates of the new heat exchanger can in fact be conveniently made of a single part, obtained by shearing, stamping and deforming a metal sheet, with no need for further welding steps. It follows that production costs are reduced and the finished piece is more resistant.

A further object of the present invention is to minimize the use of raw materials to make the heat exchanger and the cover plates in particular.

Still another object of the present invention is to enable the assembly of a plate heat exchanger pack where all the plates, including those at the ends, are made with the same stamping process, thus obtaining a pack on which the cover plates are applied as described and claimed below.

Yet another object of the present invention is to minimize thermal inertia when the exchanger is fully operational.

A further object of the present invention is to enable the use of exchange plates all with the same shape, preferably also with the same thickness, so that they can be produced with the same production methods.

These and other direct and complementary objects are achieved by the new plate heat exchanger with reinforced cover plates and method for the production of said reinforced cover plates and their assembly.

In its main components the new plate heat exchanger comprises at least one pack of exchange plates, that is, a series of stacked plates braze welded together, to confine the fluids inside, each provided with alternating ridges and depressions arranged preferably and substantially in a herringbone pattern or arranged in two directions intersecting each other, and holes for the circulation of at least two heat exchange fluids, suited to convey said two fluids in the spaces between the plates following at least two hydraulically isolated circuits.

The exchanger therefore comprises at least two separate circuits for a primary fluid and a secondary fluid, each of said two circuits being defined by a pair of said facing exchange plates, provided with said ridges and depressions.

Said exchange plates may all be of the same type or of two different types to create circuits with a different flow resistance.

Said exchange plates making up the pack are normally made of thin shaped steel sheets, braze welded together with copper or another material suitable for braze welding.

In particular, each heat exchanger plate has a substantially rectangular shape, with two longitudinal sides and two transverse sides, and where said holes for the circulation of the fluids are located near said transverse sides, close to the corners, while the remaining surface of the plate is corrugated, with said ridges and depressions that create, with a facing plate, the circuits for the circulation of fluids.

On each transverse side, a first through-hole for the circulation of fluid is made in a lowered area, while a second hole is made on a raised area, in inverted or symmetrical positions with respect to the holes in the opposite transverse side.

On the first of said heat exchanger plates making up the pack, two cover plates are mounted, where each of said cover plates is smaller than half of the surface of said first heat exchanger plate.

Said first heat exchanger plate is identical to the intermediate plates of the pack.

Each of said cover plates also has a shape and dimensions corresponding to the side portion of said first heat exchanger plate, that is, to the portion closer to a transverse edge and which comprises said holes for the circulation of fluids.

In the preferred embodiment, said cover plates have the same symmetrical shape, substantially rectangular, with four rounded corners or with the two short sides replaced by semicircles.

Each of said cover plates is furthermore provided with holes shaped and positioned so that they correspond to said holes in the heat exchanger plates.

Said cover plates are mounted at the level of said side portions of said first heat exchanger plate so that the holes in said cover plates are in a position corresponding to said holes in the stacked heat exchanger plates.

Each of these cover plates is made of steel sheet or in any case of a material normally used or in any case suitable for use in plate heat exchangers.

At the level of a hole in said cover plates there may be a metal ring, suited to ensure the seal between the cover plate and the first heat exchanger plate, and wherein said metal ring is located at the lowered area of said first heat exchanger plate where the through-hole for the fluid is made, in order to convey said fluid from the cover plate to the channels inside the heat exchanger.

Said metal ring can be joined to said cover plate, for example by welding, or, more preferably, by deformation of the cover plate itself at the hole. In other words, the edge of the hole is deformed and/or stamped so as to create said metal ring.

Said metal ring therefore has the shape of an open cylinder, joined to the cover plate. Said metal ring preferably also comprises a flange on the circular edge of said open cylinder, said flange being for example obtained by further bending the cylindrical wall itself. This embodiment has the advantages described above.

Said cover plates are positioned and centered on the first plate of the pack preferably by spot welding or arc welding or other mechanical processes in order to keep said cover plates centered with the holes in the pack and in the correct position until the braze welding step with which they are permanently welded to the pack.

Alternatively or in combination with the above, in a possible embodiment, each of said cover plates may comprise shaped tabs, protruding from the edge facing the center of said first exchange plate, and suited to be inserted in a depression made on said first exchange plate itself. This facilitates the centering and assembly of the cover plates and also guarantees proper positioning.

The tabs have a shape and dimensions that are a function of the conformation, the orientation, and the possible curvature of the depressions of said first exchange plate. Said cover plates are preferably of two types, one right and one left, according to the side of the exchanger on which they are installed.

Said cover plates furthermore act as a seat or base for the application of the fixing stud bolts and can also be suitably provided with holes, seats or coupling means in general for the installation of fixing means to the hydraulic circuit, such as fittings or the like. The present patent also relates to the production method of said cover plates and their assembly to the pack of exchange plates.

The production method comprises the following fundamental steps, the order of which are interchangeable and some of which can even be eliminated or grouped in one or more steps:

-   -   preparation and assembly of the pack of stacked heat exchanger         plates according to the known art;     -   preparation of a steel sheet, preferably in the form of a         continuous strip and possibly coupled with a copper sheet for         subsequent braze welding;     -   use of said steel sheet in at least one stamping step, where one         or more cover plates are stamped at a time;     -   use of said steel sheet in at least one drilling step, where the         holes for the circulation of the fluids are made in         pre-determined positions;     -   use of said steel sheet in at least one step for the application         of said metal rings, where they are coupled or made, for example         by spot welding, deformation, mechanical assembly or welding,         said metal rings being necessary to create a tight seal between         the cover plates and the first heat exchanger plate in the         lowered areas of the latter where the through-holes for the         circulation of each of the two fluids are made; the hermetic         seal is guaranteed by the particular shape of said metal rings         which substantially comprise an open cylinder joined to the         sheet with which the cover plates are made and preferably also a         flange;     -   use of said steel sheet in at least one shearing step, where one         or more cover plates are cut at a time;     -   use of said steel sheet in at least one bending step, where the         tabs of said cover plates are possibly created;     -   plate heat exchanger assembly, where said cover plates are         applied to the two side portions of the first heat exchanger         plate of said pack of heat exchanger plates; said assembly step         provides, for example, as mentioned, for the spot welding or arc         welding or other mechanical positioning/fastening process of the         cover plates to the first heat exchanger plate so that the         respective holes are centered.

Said stamping, drilling and shearing, as well as the bending step of the possible tabs and application/formation of said metal rings, can be carried out in separate and distinct steps or they can be carried out in one or more grouped steps.

For example, said stamping, drilling and shearing steps can all be performed in a single step and processing station.

The characteristics of the present invention will be better clarified by the following description with reference to the drawings, attached by way of a non-limiting example.

FIG. 1 shows a three-dimensional view of the completely assembled plate heat exchanger (1), while FIGS. 2 and 3 show a section view and a plan view respectively.

FIG. 4 shows a three-dimensional view of cover plates (21) to be installed on one side of a heat exchanger plate pack (10), for example on the left.

FIG. 5 shows a three-dimensional view of cover plates (22) to be installed on one side of a heat exchanger plate pack (10), for example on the right.

In FIGS. 1 to 5 each of said cover plates (21, 22) has an asymmetrical shape, according to a first possible embodiment. In contrast, a preferred embodiment of said cover plates (21, 22) is schematized in FIG. 6, where said cover plates (21, 22), whether they are on the right or on the left, have a symmetrical, substantially rectangular shape where the shorter sides are made up of semicircles.

FIG. 7 shows a section view of a cover plate (21, 22) at the level of the hole (231) made in the cover plate (21, 22) itself, where the metal ring (3′) obtained by deformation and/or stamping of the edge (232) of the hole (231) itself can be seen. In this particular embodiment, said metal ring (3′) is a single solid piece with said cover plate (21, 22), thus without the need for welding or mechanical joining in general.

The plate exchanger (1) comprises in its main parts at least one pack of exchange plates (10) that is a series of superimposed plates (101) in a pack.

Each of said exchange plates (101) in turn comprises alternating ridges (102) and depressions (103), arranged preferably and substantially in a herringbone pattern or arranged in two intersecting directions.

Each of said exchange plates (101) is also provided with two pairs of through-holes (104) for the passage of at least two heat-transfer fluids, said holes (104) being made at the level of lowered and raised areas alternately positioned on the two sides of the plates (101), to convey said two fluids into the spaces between the plates following at least two hydraulically isolated circuits.

Said exchange plates (101) forming said pack (10) are normally made of thin shaped steel sheets.

Each exchange plate (101) has a substantially rectangular shape, with two longitudinal sides (105) and two transverse sides (106), and where said fluid through-holes (104) are formed near said transverse sides (106), close to the corners.

Two cover plates (21, 22) are mounted on the first exchange plate (107) of said pack (10), each shaped in correspondence with the transverse side for which it is intended.

Each of said cover plates (21, 22) has a shape and dimensions substantially corresponding to the side portions of said first exchange plate (107) close to the two transverse sides (106) and comprises a pair of said holes (23, 231) corresponding to said holes (104) in the exchange plates (101).

In the example of FIG. 6, each of said cover plates (21, 22) has a symmetrical shape, so that they can be mounted either on the right or the left of the pack (10).

Each of said cover plates (21, 22) is made of steel sheet or in any case of material normally used or in any case suitable for use in plate heat exchangers.

As can be seen from FIGS. 1, 2 and 3, said cover plates (21, 22) also act as a seat or base (27) for the application of the fixing stud bolts and can also be suitably provided with holes, seats or coupling means in general for the installation of fixing means to the hydraulic circuit, such as fittings or the like.

At least one hole (231) in one or both of said cover plates (21, 22) may be provided with a metal ring (3, 3′), necessary to create a hermetic seal between said cover plates (21, 22) and said first exchanger plate (107) at the lowered area in which the through-hole (104) for a fluid is made, in order to convey said fluid from the cover plate (21 22) to the internal channels of the exchanger.

In the embodiment in FIGS. 4 and 5, said metal ring (3) is for example applied at the level of said hole (231) in the cover plate (21, 22) and constrained/coupled by means of spot welding and/or deformation and/or welding and/or mechanical assembly in general. Said ring (3) is therefore a distinct piece from the cover plate (21, 22) and joined to it during the production/assembly step.

In the specific and preferred but not exclusive embodiment in FIG. 7, said metal ring (3′) is a single piece with respect to the cover plate (21, 22) being obtained by means of deformation and/or stamping of the edge (232) of the hole (231) in the cover plate (21, 22) itself.

In this case, the edge (232) of said hole (231) in said cover plate (21, 22) is bent towards one side of the cover plate (21, 22) itself, that is, the side intended to be turned towards said first exchanger plate (107), thus forming said metal ring (3′) in a single solid piece with said cover plate (21, 22).

Said metal ring (3′) is therefore substantially formed by an open cylinder. The embodiment in FIG. 7 shows how said metal ring (3′) can further comprise a flange (31′) suited to ensure a tight seal in the subsequent assembly of each cover plate (21, 22) to the first exchange plate (107) of the pack (10).

Said flange (31′) is also preferably obtained by deformation/bending.

Each of said cover plates (21, 22) may also comprise, but not necessarily, shaped tabs (24, 25), protruding from the edge (26) facing the center of said first exchange plate (107), and suited to be inserted in one of said depressions (103) of said first exchange plate (107) itself.

Therefore, with reference to the preceding description and the attached drawings the following claims are made. 

The invention claimed is:
 1. A plate heat exchanger (1) comprising: a pack (10) of superimposed heat exchanger plates (101) provided with alternating ridges (102) and depressions (103), said alternating ridges and depressions defining, together with the ridges (102) and depressions (103) present on another facing heat exchanger plate (101), circuits for the heat exchange fluids, and through-holes (104) configured to convey two of the heat exchange fluids in spaces between the heat exchanger plates following at least two hydraulically isolated circuits, wherein each heat exchanger plate (101) is rectangular in shape, wherein the heat exchanger comprises two cover plates (21, 22) mounted on a first one (107) of said heat exchanger plates (101), wherein a surface area of each of said two cover plates (21, 22) is smaller than half the surface area of said first heat exchanger plate (107) and wherein each of said two cover plates (21, 22) further comprises: a pair of second holes (23, 231) shaped and positioned to correspond to said through-holes (104) in the heat exchanger plates; and a metal ring (3, 3′), positioned to surround one of said second holes (231) and on a lower area of said first heat exchanger plate (107) where one of the through-holes (104) for one of the heat exchange fluids is made, wherein said metal ring (3, 3′) is adapted to guarantee a hermetic seal between one of said cover plates (21 22) and said first heat exchanger plate (107).
 2. The plate heat exchanger (1) according to claim 1, wherein an edge (232) of the one of said hole (231) in one of said cover plates (21, 22) is bent towards one side of the one of said cover plates (21, 22), forming said metal ring (3′) in a single solid piece with the one of said cover plates (21, 22).
 3. The plate heat exchanger (1) according to claim 2, wherein the edge of said metal ring (3′) is further bent outwardly to form a flange (3 G).
 4. The plate heat exchanger (1) according to claim 1, wherein a shape and size of said two cover plates (21, 22) correspond to side portions of said first heat exchanger plate (107), the side portions comprising said through-holes (104) and being located in proximity to the transverse edges (16).
 5. The plate heat exchanger (1) according to claim 4, wherein each of said two cover plates (21, 22) has a symmetrical shape, so that each of said two cover plates can be mounted either on a right side or a left side of the pack (10).
 6. The plate heat exchanger (1) according to claim 1, wherein each of said two cover plates (21, 22) comprises one or more shaped tabs, which project from an edge (24) facing a center of said first one (107) of said heat exchanger plates (101) and is configured to be inserted in one of said depressions (103) provided on said first one (107) of said heat exchanger plates (101).
 7. The plate heat exchanger (1) according to claim 1, wherein said two cover plates (21, 22) provide a seat or base (27) for an application of fixing stud bolts and is provided with holes, seats or coupling means for installation of means for fixing said two cover plates (21, 22) one of the at least two hydraulically isolated circuits.
 8. The plate heat exchanger (1) according to claim 1, wherein said first one (107) of said heat exchanger plates is equal to at least one of the other heat exchanger plates (101) forming the pack (10).
 9. The plate heat exchanger (1) according to claim 1, wherein said heat exchanger plates (101) are all identical or of two different types in order to define hydraulic circuits with different flow resistance.
 10. A method of making the plate heat exchanger (1) according to claim 1, comprising the following steps: preparing and assembling said pack (10) of superimposed heat exchanger plates; preparing a steel sheet; performing a stamping step of said steel sheet, wherein one or more of said cover plates (21, 22) are stamped at a time; drilling said steel sheet forming said pair of second holes in pre-determined positions; applying or forming said metal rings (3) on said steel sheet; shearing said steel sheet in at least one shearing step to cut said cover plates (21, 22); and assembling said plate heat exchanger (1), wherein said cover plates (21, 22) are applied to two side portions of the first heat exchanger plate (107) of said pack (10) of heat exchanger plates.
 11. The method according to claim 10, further comprising a step of bending said steel sheet to form tabs of said cover plates (21, 22).
 12. The method according to claim 10, further comprising a step of coupling said steel sheet with a copper sheet suitable for subsequent braze welding.
 13. The method according to claim 10, wherein two or more of said steps are grouped and carried out in a same station. 